Hitherto, there has been known an art in which images of partition lines on the left and right of a travel lane currently traveled by a vehicle are recognized to display the forward image with a guide line superimposed at the middle between the images of the partition lines on the left and right of the travel lane on a forward image in which a scene ahead of the vehicle is captured (see PTL 1 (Japanese Patent Application Publication No. 2008-309529 (JP 2008-309529 A))). Since the guide line is superimposed at the middle between the recognized images of the partition lines on the forward image, the guide line can indicate the center position of the travel lane in the width direction with high accuracy.